IntelliWheels automatic gear-shifting wheels represent a significant paradigm shift as the first ultra-light, affordable, and intuitive way to mke pushing a wheelchair easier. The manual wheelchair user (mWCU) still pushes the hand rims in any direction, however the hand rims drive the transmissions (located in each wheel hub), which in turn, drive the wheels. Similar to the way that people ride bicycles, gear shifting allows peopl to move up and down hills, over rough terrain, and over long distances in a more efficient way. There are 2.7 million mWCUs in the United States, and research shows that shoulder pain is reported in up to 70% of them. Shoulder pain has been directly linked to difficulty in tasks of daily living, and geared wheels have been shown as an effective way to reduce the levels of pain reported. IntelliWheels' affordable geared wheels will provide wheelchair users of varying disability levels a mobility option to positively change their interaction with their wheelchair. Current options for mWCUs experiencing shoulder pain include powered wheelchairs and power assist wheels, which are heavy, expensive, and provide more assistance than is necessary for most mWCUs. IntelliWheels will offer lightweight, affordable options for mWCUs to remain independently mobile. During the 24-month project period, IntelliWheels will design and fabricate market ready version of a 3-speed automatic shifting and 3-speed manual shifting wheelchair wheel. The prototypes will be designed to meet target specifications: weight less than 12 lbs (<6 lbs for manual shifted configuration), battery life of at least 24 hours (for the automatic shifter), and manufactured to a last at least 5 years of life. Manufacturing costs must be low enough to price them competitively with high-end single speed wheels and be reimbursable under Medicare code E2227. The prototypes will be put through rigorous bench-top ISO specified fatigue tests. User feedback through focus groups and end user demonstration testing will be used to determine the performance and marketability of the IntelliWheels design. Finally, biomechanical analysis of the push mechanics in different gears will be conducted to investigate the upper extremity joint loads, and their effect on joint pain an tasks of daily living.